Method and system for forming strings of pocketed coil springs with traction mechanism

ABSTRACT

A string ( 12 ) of pocketed coil springs ( 14 ) is formed by inserting compressed springs between upper and lower plies of a folded, preferably thermally weldable fabric ( 16 ). The springs are maintaned in a compressed configuration while a longitudinal seam ( 54 ) joins the free edges of the thermally welded fabric ( 16 ) together. Subsequently, the compressed springs ( 14 ) are allowed to relax into an expanded configuration after which a transverse seam ( 80 ) is formed in the fabric ( 16 ) between the adjacent springs ( 14 ) thereby encapsulating each spring ( 14 ) within a fabric pocket ( 86 ). The string ( 12 ) of pocketed coil springs ( 14 ) is advantageously formed without the need for reorienting the springs ( 14 ) after being inserted between the plies ( 24,26 ) of the fabric ( 16 ) and thereby avoiding the disadvantages and complications associated with turning or reorienting the pocketed coil spring ( 14 ).

This is a continuation-in-part of U.S. patent application Ser. No.09/884,535, filed Jun. 19, 2001, now U.S. Pat. No. 6,591,436, which inturn was a continuation-in-part of U.S. patent application Ser. No.09/595,755, filed Jun. 16, 2000, now U.S. Pat. No. 6,499,275, which inturn was a continuation-in-part of U.S. patent application Ser. No.09/353,483, filed Jul. 13, 1999, now U.S. Pat. No. 6,336,305, and whichin turn was a continuation in part of U.S. patent application Ser. No.09/293,221, filed Apr. 16, 1999, now abandoned, each of which are herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to spring assemblies for mattresses,cushions and the like, and, more particularly, to a method and systemfor making a string of connected individually pocketed coil springs formattresses, cushions, spring units and the like.

Pocketed coil springs are often referred to as a Marshall constructionin which each coil spring is encased within its own fabric sack orpocket. The sack or pocket is typically defined between two plies of afabric strip connected together at intervals along transverse linesspaced along the strip. The two-ply fabric strip is generally formed byfolding a strip of double width fabric upon itself along a longitudinalcenterline, leaving the overlapped plies along the unjoined oppositeedges of the strip to be connected to each other along a longitudinalseam to close the pockets defined between the transverse lines ofconnection after the springs are inserted between the plies.

A variety of techniques have evolved for the manufacture of pocketedsprings, some contemplating the creation of the pockets within thefabric plies prior to insertion of the wire spring and otherscontemplating the insertion of compressed wire springs between the pliesof the strip and the subsequent creation of the pockets by stitching orotherwise joining the two plies to each other along transverse linesbetween adjacent springs. Irrespective of the technique used, the fabricis closed around the spring after the insertion of the spring, usuallyby stitching or welding the two plies together along a line parallel tothe free edges of the plies. Joining the plies together by stitching haslargely been replaced in more recent times by the use of a heatsensitive fabric and ultrasonic welding techniques. Examples of knownsystems and techniques for manufacturing strings of pocketed coil springare disclosed in U.S. Pat. Nos. 4,439,977; 4,234,983; and 5,613,287,each of which are incorporated herein by reference.

Specifically, in U.S. Pat. No. 4,439,977, a method and apparatus aredisclosed for making coil springs enclosed within individual pockets inan elongate fabric strip comprised of two overlying plies capable ofbeing thermally welded together. The fabric strip is fed along a guidepath during which compressed springs are inserted between the plies withthe axes of the springs substantially normal or perpendicular to theplanes of the plies. Thereafter, the fabric plies are thermally weldedtogether longitudinally and transversely while the spring remainscompressed to form a string of pocketed coils. After thermal welding,the pocketed coils are passed through a turner assembly during which thesprings are reoriented typically about 90° within the fabric pockets topositions wherein the axes of the springs are transverse to the fabricstrip.

In general, known systems and methods for producing strings of pocketedcoil springs have not been completely satisfactory due in large part tothe difficulties in handling and processing the fabric and springs in amass production, efficient environment. The ability to process,manipulate, advance and incorporate the fabric and springs into a stringin an efficient, quality-controlled manner and without operatorintervention is crucial to such a system and method. In some instances,the fabric may become tangled or difficult to neatly feed and advancewhich requires operator correction and down time.

One additional disadvantage of the method of manufacturing pocketed coilsprings shown in U.S. Pat. No. 4,439,977 is that during the turningprocess, springs tend to become entangled or hooked together and do notachieve their proper positions. As such, additional and costly labor isrequired to reorient and disentangle the springs to place them intotheir desired configurations and orientations. Even if the springs donot become entangled or hooked, difficulties may still arise incorrectly aligning them to their desired positions with the longitudinalaxes of the springs being substantially parallel to one another and thetransverse seams defining individual pockets.

Another common problem with this type of operation is that during theturning of the pocketed springs, whether or not the springs becomehooked or entangled and the turning process is successful, the fabricsurrounding the spring is often damaged, torn, punctured or the like. Inone form, the springs are beaten by paddles as disclosed in U.S. Pat.No. 4,439,977 to effect the turning of the spring within the pocket.Obviously, the repeated beating on the pocket with the paddles may causesignificant damage to the fabric material and prove to be unreliable toaccurately position the spring within the fabric pocket. When thishappens, the damaged pocket should be repaired or removed from thestring thereby interrupting the process and requiring significantoperator intervention and down time for the production of pocketed coilsprings.

Therefore, a need exists for a method and system for forming strings ofpocketed coil springs which overcomes the above described disadvantagesof the prior art and does not require operator intervention to handlethe fabric or springs. Further, the turning of the springs within thepockets for alignment of the spring axes in a generally parallel andordered arrangement and operator intervention to unhook or disentanglethe springs and repair the damaged fabric surrounding the springs arepreferably avoided. Further, a need has always existed to providecommercially viable methods and systems for producing strings ofpocketed coil springs which are cost and labor effective by requiring aminimal amount of labor intervention and associated resources.

SUMMARY OF THE INVENTION

The present invention overcomes the above described and otherdisadvantages in the prior art by providing an improved method andsystem for producing strings of pocketed coil springs which areeffective in performance, yet cost effective in that they require aminimum amount of materials and labor. The manner in which the springsare inserted into the fabric, the handling of the fabric and springs,the formation of the pocket, insertion of the springs and operatorinvolvement generally, according to this invention avoid the need forturning or repositioning the springs within the pockets while stillproviding an efficient and reliable manufacturing system and associatedmethod for reliably producing consistently aligned springs withinundamaged fabric pockets.

The present invention preferably begins with the insertion of acompressed coil spring between upper and lower plies of a thermallywelded fabric. The present invention is a continuous production processsuch that the fabric is indexed or pulled past a spring insertionstation so that the compressed springs are individually inserted betweenthe plies of the folded fabric at spaced intervals as the fabric passesthe spring insertion station. In one alternative embodiment of theinvention, the fabric is controlled and advanced by spikes which engagethe fabric for processing without damaging the fabric.

The springs are maintained in a compressed configuration between theplies of the fabric while a longitudinal seam is formed in the fabric tojoin the two plies together proximate free edges of the plies oppositefrom a longitudinal fold line of the fabric. Since the fabric is athermally weldable material, preferably the longitudinal seam is formedby a cooperating thermal weld head and anvil combination. After thespring has advanced past the longitudinal weld station, it is allowed torelax and expand within the fabric into an upright position in which alongitudinal axis of the spring is generally perpendicular to thelongitudinal seam of the fabric. Preferably, the relaxation andexpansion of the springs within the fabric are controlled by a pair ofrotating members on opposite sides of the springs according to variousalternative embodiments of this invention. The rotating members inpresently preferred embodiments may be a pair of oppositely rotatingwheels with axes of rotation generally parallel to the longitudinal axesof the springs. The wheels include a plurality of arcuate-shapedrecesses which combine to partially surround each spring during theexpansion. Alternatively, the rotating members may include a pair ofbands each passing over a pair of spaced rollers. The bands may includeprojecting members to engage and advance the fabric while the springsare expanding and the fabric is advancing. The fabric and springs passbetween the bands and a separation distance between the bands increasesin a downstream direction to thereby control the expansion of thesprings between the bands. The springs are preferably supported duringtheir expansion into an upright position.

After the springs have expanded within the fabric, individual pocketsare formed preferably by a transverse weld head sealing the fabricbetween each of the springs generally parallel to the spring axes. Thetransverse seams are formed in the fabric to complete the individualpockets for the individual springs. Finally, a pair of opposing androtating transport wheels indexes or moves the string of pocketedsprings forwardly thereby advancing the fabric and enclosed springsthrough the various stations as described.

Advantageously, the orientation of the springs remains generallyunchanged throughout the pocketing process so that reorientation,turning or the like of the springs within the pockets is avoided.Moreover, the longitudinal seam formed in the fabric is positioned on aside face of the individual spring pockets in the resulting string ofpocketed coil springs thereby avoiding the problem known in the art as“false loft”. False loft occurs when the longitudinally extending seamsmaintain the cover material at a certain distance away from the ends ofthe springs so that when the mattress is first purchased, this distanceis fairly uniform. However, after the mattress or cushion has been inuse for a period of time, the longitudinally extending seams or otherexcess fabric in the pocketed coil string may become crushed thusleaving areas or regions of depression. With continued use of themattress or cushion, the entire support surface of the mattress orcushion will similarly be crushed and will appear substantially flat. Auser may not realize the source of this phenomenon and consider it to bea defect in the mattress or cushion.

The problem of false loft is thereby avoided in the present invention bypositioning the longitudinal seam of the string of springs on a sidethereof while still avoiding the need to turn or reorient the individualsprings within the pockets and the resulting damage to the fabric andother associated problems.

Another feature of this invention which also aids in the reduction offalse loft and related problems is particularly useful for barrel shapedsprings or other such springs which have a non-linear profile. With suchsprings, the transverse seam between adjacent springs in the string isshaped to conform to the profile of the springs and thereby produce atighter, more conforming fabric pocket around the spring to avoidbunching or excess loose fabric around the spring.

BRIEF DESCRIPTION OF THE DRAWINGS

The objectives and features of the invention will become more readilyapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a top plan view of a schematic representation of a system andassociated method according to a first embodiment for producing a stringof pocketed coil springs of this invention;

FIG. 2 is a side elevational view of the system and method of FIG. 1;

FIG. 3 is a view similar to FIG. 1 of a second presently preferredsystem and associated method according to this invention;

FIG. 4 is a side elevational view of the system and method of FIG. 3;

FIG. 5 is a perspective view of a string of pocketed coil springsproduced according to this invention;

FIG. 6 is a cross-sectional view of an individual coil spring encasedwithin a fabric pocket as taken along line 6-6 of FIG. 5;

FIG. 7 is a side elevational view of a string of pocketed coil springsproduced according to an alternative embodiment of this invention;

FIG. 8 is a partial perspective view of a weld head used to weld atransverse seam in the string of FIG. 7;

FIG. 9 is a perspective view of a third presently preferred system andassociated method according to this invention;

FIGS. 10, 10A and 10B are views of an alternative embodiment of thesystem and associated method of FIGS. 3 and 4; and

FIGS. 11 and 12 are views of a further alternative embodiment of a beltutilized in the system and associated method of FIGS. 3 and 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a first presently preferred embodiment of a system10 and associated method for forming a string 12 of pocketed coilsprings 14 according to this invention is shown. Fabric 16, preferablythermally weldable as is well known in the art, is fed from a supplyroll 18 around a roller 20 as shown in FIG. 1. Alternatively, the fabric16 could be cotton or another suitable material. The fabric 16 is foldedgenerally in half longitudinally about a longitudinal fold line 22 whichcoincides approximately with a longitudinal centerline of the fabric 16.The fabric 16 is folded about the longitudinal fold line 22 to produce afirst, upper ply 24 and a second, lower ply 26 of fabric 16 each with afree edge 28 spaced from the longitudinal fold line 22. The foldedfabric 16 passes upper and lower input rollers 30, 32 prior to enteringa spring insertion station 34. The rollers 20, 30 and/or 32 may berotationally driven. While the fabric 16 is shown in the figures asbeing a single sheet and folded about the longitudinal fold line 22 toform the plies of fabric 24, 26, it should be readily understood thatthe plies 24, 26 could be produced from multiple, distinct sheets offabric that are joined together at a longitudinal seam instead of thelongitudinal fold line 22.

The spring insertion station 34 includes a reciprocating insertionplunger 36 having a cup-shaped spring receiving leading end 38 toreceive therein a compressed coil spring 14. The plunger 36 extends toinsert the compressed spring 14 between the plies 24, 26 and retracts toreceive another compressed spring 14 for subsequent insertion. Thespring 14 is formed according to any know spring forming apparatus,including the system disclosed in Swiss Patent Application Serial No.02187/00, filed Nov. 10, 2000 and hereby incorporated by reference inits entirety.

The formed spring 14 is compressed and loaded onto the spring insertionplunger 36 and the fabric 16 is folded according to one of any number ofwell known systems and methods for doing so. Alternatively, the springinsertion station 34 may comprise two U-shaped profiles which keep thespring 14 compressed and lead the springs 14 inside the folded fabric16. In this method, the spring 14 is held with a horn (not shown) whilethe profiles return.

As the fabric 16 advances through the system 10, the springs 14 insertedbetween the plies 24, 26 are maintained in a compressed configurationbetween upper and lower support plates 40, 42 on the upper and lowerfaces, respectively, of the fabric 16 as particularly shown in FIGS. 1and 2. Preferably, the support plates 40, 42 are centered between thefree edges 28 and longitudinal fold line 22 of the fabric 16 and mayinclude a wider region 44 proximate the spring insertion station 34which tapers downwardly to a region of smaller separation 46 between theplates 40, 42 as the fabric 16 and springs 14 advance through subsequentportions of the system 10.

Additionally, a plurality of spaced alignment wheels 48 which aremounted for rotation proximate the longitudinal fold line 22 and freeedges 28 of the fabric 16 control and direct the movement of the fabric16 through the system 10. The alignment wheels preferably include aplurality of spikes or projections 50 which engage the fabric 16 tomaintain the movement of the fabric 16 in an aligned orientation withrespect to the various stations and components of the system 10.

A longitudinal seam forming station 52 is located downstream from thespring insertion station 34 proximate the free edges 28 of the fabric16, as shown in FIGS. 1 and 2. After the compressed springs 14 areinserted between the plies 24, 26, the longitudinal seam forming station52 joins the upper and lower plies 24, 26 of the fabric 16 togetherproximate their respective free edges 28 thereby initially enclosing thesprings 14 within the fabric 16. In a presently preferred embodiment, alongitudinal seam 54 is formed between a thermal weld head 56 whichreciprocates downwardly and upwardly for cooperating welding engagementand disengagement, respectively, relative to an anvil 58 positionedbelow the lower ply 26. The reciprocating weld head 56 and anvil 58cooperate to form the longitudinal seam 54 in the fabric 16 by weldingthe respective plies 24, 26 together ultrasonically, thermally, or thelike as is well known by those skilled in the art. Alternatively, theanvil 58 is moved reciprocally while the thermal weld head 56 remainsstationary. The springs 14 remain compressed during the formation of thelongitudinal seam 54 and weld with their longitudinal axes 60 generallyperpendicular to the longitudinal seam 54. It should be appreciated thatother means for joining the plies 24, 26 together to form the seams suchas stitching, staples, or other means are well within the scope of thepresent invention.

A first transport station 62 is located downstream from the longitudinalseam forming station 52 and, in a presently preferred embodiment,includes four transport bands 64. Each band 64 passes over spacedforward and trailing rollers 66, 68, at least one of which isrotationally driven. A first pair of bands 64 a at the first transportstation 62 contacts the fabric 16 proximate the longitudinal fold line22 passing therebetween. Another pair 64 b of transport bands 64contacts the fabric 16 proximate the longitudinal seam 54 as shown inFIGS. 1 and 2. As the bands 64 pass around the spaced rollers 66, 68 incontact with the fabric 16, the fabric 16 is pulled from the supply roll18 through the upstream stations and is advanced toward a downstreamspring expansion station 70.

The compressed springs 14 are permitted to relax and expand within thefabric 16 at the spring expansion station 70. In a first embodiment, theexpansion of the springs 14 is controlled by a pair of oppositelyrotating rotational members 72 on opposite sides of the springs 14 asshown in FIG. 1. An axis of rotation 74 of each of the rotationalmembers 72 according to the first presently preferred embodiment of FIG.1 is generally parallel to the longitudinal axes 60 of the springs 14.Each rotational member 72 includes a plurality of arcuate-shapedrecesses 76, each of which combine with a similarly configured recess 76in the corresponding rotation member 72 on the opposite side of thespring 14 to partially surround each spring 14 and thereby control theexpansion thereof. Additionally, the rotational members 72 assist inadvancing the springs 14 and fabric 16 toward a transverse seam formingstation 78 located downstream therefrom.

The transverse seam forming station 78 forms a transverse seam 80 in thefabric 16 between each of the adjacent springs 14 which have expandedwithin the fabric 16 from their compressed configuration. Preferably,the transverse seam forming station 78 includes a transverse seam weldhead 82 and a cooperating transverse seam anvil 84 located on oppositesides of the forming string 12 of pocketed coil springs 14 from eachother, as shown in FIG. 1. As the springs 14 advance toward and throughthe transverse seam forming station 78, the fabric 16 between thesprings 14 is joined together thereby completing individual pockets 86for each of the springs 14 and enclosing the springs 14 within thefabric 16. Once again, it should be readily appreciated that other meansfor forming the transverse seam 80 such as stitching, staples or thelike may be used within the scope of this invention. While thetransverse seam 80 is formed, the fabric 16 is needed or gathered. Assuch, the string 12 of pocketed coil springs 14 must give in or contractsomewhat to accommodate the seam forming process. This can beaccomplished with an active mechanism such as a driven transport systemor with in a passive manner such as friction between the fabric 16 andthe transport rotational members 72.

The longitudinal axes 60 of the springs 14 remain generally parallel tothe transverse seams 80 in the fabric 16. However, due to the expansionof the springs 14, the longitudinal seam 54 formed at the free edges 28of the fabric 16 is positioned generally on a side face 88 of the string12 of pocketed coil springs 14 between top and bottom ends 90, 92 of thepocketed coil spring 14 as shown particularly in FIGS. 5 and 6. With thelongitudinal axes 60 of the springs 14 generally aligned and parallelwith one another within individual fabric pockets 86, the presentinvention avoids the need for turning the springs 14 within the fabricpockets 86 as is required in many prior art systems.

Referring to FIGS. 5 and 6, the longitudinal seam 54 preferably becomesattached to the pockets 86 when the transverse seam 80 is formed by thetransverse seam forming station 78. As such, in the region of the fabric16 proximate the transverse seam 80, four layers of fabric 16 are weldedtogether at the transverse seam forming station 78. It should beappreciated that there are other methods to fix the seam 80 in thismanner, for example, the longitudinal seam 54 could be positioned andtacked or fixed to the side 88 of the pockets 86 prior to entering thetransverse seam forming station 78 even if it is not welded to thepockets 86 with the transverse seam 80. Further, the longitudinal seam54 may be located anywhere between the top and bottom of the stringalthough it is shown in the drawings as approximately in the middlethereof.

A downstream or second transport station 94 preferably includes a pairof oppositely rotating transport wheels 96 each with an axis 98 ofrotation generally parallel to the longitudinal axes 60 of the springs14. A plurality of arcuate recesses 100 on the periphery of thetransport wheels 96 cooperate to at least partially surround thepocketed springs 14 and advance them from the upstream transverse seamforming station 78 for discharge and subsequent packaging, storage orprocessing into a mattress, cushion or innerspring unit.

An alternative embodiment of this invention is shown in FIGS. 3 and 4and components of the system 10 of FIGS. 3 and 4 which are similar tothose of the first embodiment shown in FIGS. 1 and 2, are identified byidentical reference numerals and the previous detailed description withrespect to those items provided hereinabove is likewise applicable tothe embodiment of FIGS. 3 and 4. The second presently preferredembodiment shown in FIGS. 3 and 4 includes divergent transport bands 102located above and below the fabric 16 and enclosed springs 14 at thespring expansion station 70. The transport mechanism could be embodiedwith wheels as in FIGS. 1 and 2 and/or transport bands as in FIGS. 3 and4 which are located on the top and bottom of the string or the lateralside surfaces as desired. Each of the transport bands 102 of FIGS. 3 and4 and alternative embodiments thereof, pass over forward and trailingrollers 104, 106, as shown particularly in FIG. 4. Furthermore, aseparation distance between the transport bands 102 increases in adownstream direction such that the bands 102 are preferably angled amaximum of about 10° (α in FIG. 10), although the angle α is largelydependent upon the height of the pocket, but preferably less than 45°.The orientation of the bands 102 thereby permit the controlled expansionof the springs 14 positioned in the fabric 16 between the transportbands 102. The relaxed and expanded springs 14 are then advanced to thedownstream transverse seam forming station 78 so that the transverseseam 80 may be positioned between the adjacent springs 14 to completethe individual fabric pockets 86.

An alternative embodiment of this invention is shown in FIGS. 10, 10Aand 10B. Specifically, the alternative embodiment relates to a modifiedform of the transport bands 102 a as previously shown and described withrespect to FIGS. 3 and 4. The modified transport bands 102 a includetraction means in the form of a plurality of projections or spikes 103projecting from the bands 102 a. The spikes 103 may be arranged in asingle row 105 and aligned with the direction of travel of the band 102a as shown in FIG. 10B. Alternatively, a plurality of rows 105 of spikes103 may be aligned with the direction of travel of the band 102 a (FIG.10A). Advantageously, the spikes 103 enhance the adhesive ability ortraction between the bands 102 a and the string 12 without confining thesprings 14 thereby allowing them to relax and expand within the fabric16.

In one presently preferred embodiment, the spikes 103 are about 5.0millimeters in length and spaced about 10.0 millimeters from eachadjacent spike 103 in the common row 105. With respect to the multiplerow 105 embodiment of FIG. 10A, seven rows 105 of spikes 103 may bespaced across a 180.0 millimeter wide band 102 a with a 20.0 millimetergap between adjacent rows 105.

A further alternative embodiment of this invention is shown in FIGS. 11and 12. Specifically, this alternative embodiment relates to a modifiedform of the transport bands 102 b as previously shown and described withrespect to FIGS. 3 and 4. The modified transport bands 102 b includetraction means in the form of a plurality of projections or nibs 107projecting from the bands 102 b. The nibs 107 may be arranged as shownin FIG. 11 in which each row 105 is spaced about 8.5 mm from an adjacentrow and the nibs 107 in each row are spaced about 10.5 mm apart andaligned with the direction of travel of the band 102 b as shown in FIG.11. Advantageously, the nibs 107 enhance the adhesive ability ortraction between the bands 102 b and the string 12 without confining thesprings 14 thereby allowing them to relax and expand within the fabric16.

In one presently preferred embodiment, each nib 107 is about 3.0millimeters in height and includes an upper cylindrical shank 109 ofabout 2.0 mm in diameter having traction grooves 111 and projectingupwardly from a base 113 having about a 5.0 mm diameter bottom and aramp angle β of about 45°. The band 102 b and nibs 107 in one embodimentare PVC and polyester fabrics available as model numberTPF911200-250/NONEX EM 10/200+20 FG AS from Ammeraal Beltech inSwitzerland (www.ammeraal-beltech.ch).

While specific embodiments for the traction means and arrangements forthe spikes 103 and nibs 107 are shown in FIGS. 10, 10A, 10B, 11 and 12,it should be appreciated that other means, arrangements, and mechanismscould be employed within the scope of this invention. The traction meansimprove the traction and interaction between the bands 102 a, 102 b andthe fabric 16 and enclosed springs 14 while the compressed springs 14are relaxing and expanding within the fabric 14 into an uprightposition. Moreover, the traction means, spikes 103, nibs 107,projections 50 (FIGS. 1-4) or similar mechanism could be employed atother stations or locations along the pocketed spring formation system10 and method of this invention or other related systems and methods toimprove the control of the springs 14 and/or the advance of the fabric16 or strings 12.

An additional feature of this invention is shown in FIGS. 7 and 8 and isparticularly adapted for use in constructing strings 12 of pocketed coilsprings 14 a having a barrel shaped configuration as shown in FIG. 7.Barrel shaped springs 14 a are well known in the industry and include aprofile 108 in which the middle turns 110 of the spring 14 a have agreater diameter than the top turn 112 and bottom turn 114 of the spring14 a. For example, the top and bottom turns 112, 114 of the barrelshaped spring 14 a may have a diameter of about 1.625 inches and themiddle turn 110 have a diameter of about 2.5 inches. When barrel shapedsprings 14 a are used in the string 12, the transverse seam 80 aadjacent to the spring 14 a conforms to the profile 108 of the spring 14a as shown in FIG. 7. With the transverse seam 80 a conforming to theprofile 108 of the spring 14 a encased in the pocket a tighter pocket isproduced with less loose fabric 16 in the string 12 and a better overallproduct, especially with springs 14 a having a non-linear profile. Withbarrel shaped springs 14 a, the transverse seam 80 a adjacent theretohas a concave shape and because the transverse seam 80 a is locatedbetween adjacent barrel shaped springs 14 a the seam 80 a may have apair of outwardly facing concave shapes forming an X or similarconfiguration.

A weld head 82 a suitable for forming the transverse seam 80 a is shownin FIG. 8 in which a number of studs 116 are arranged in the patternshown so that adjacent studs 116 proximate the top and bottom of theweld head 82 a are spaced farther apart than those in the middle toconform with the profiles 108 of the adjacent barrel shaped springs 14a. Although the transverse seam 80 a of FIG. 7 is symmetric, otherconfigurations are contemplated within the scope of this invention.Moreover, in another sense, this feature of the invention is useful notonly for barrel shaped springs 14 a to form a tighter, more conformingfabric pocket, but also for springs having a non-linear profile ingeneral such as the barrel shaped springs and hour glass shaped springsin which the middle turns have a lesser diameter than the top and bottomturns.

An additional alternative embodiment of this invention is shown in FIG.9 and components of the system 10 which are similar to those of theother embodiments are identified by identical reference numerals. Theembodiment shown in FIG. 9 includes the preferably thermally weldablefabric 16 which is folded generally in half longitudinally about thelongitudinal fold line 22 which coincides approximately with alongitudinal centerline of the fabric 16. The fabric 16 is folded aboutthe longitudinal fold line 22 to produce a first, upper ply 24 and asecond, lower ply 26 of fabric 16 each joined to one another at thelongitudinal fold line 22 and having a free edge 28 spaced from thelongitudinal fold line 22. The folded fabric 16 enters the springinsertion station 34 at which the compressed spring 14 is insertedbetween the plies 24, 26 of the fabric 16 as previously described withrespect to the other embodiments of this invention.

As the fabric 16 initially advances through the system 10, the springs14 inserted between the plies 24, 26 are maintained in a compressedconfiguration, as for example between upper and lower support plateswhich have been omitted from FIG. 9 for clarity.

The fabric 16 advances to the longitudinal seam forming station 52 whichis located downstream from the spring insertion station 34 and isproximate the free edges 28 of the fabric 16. The longitudinal seamforming station 52 joins the upper and lower plies 24, 26 of the fabric16 together proximate their respective free edges 28 to therebyinitially enclose the springs 14 within the fabric 16. The longitudinalseam 54 is formed between the thermal weld head 56 which reciprocatesdownwardly and upwardly for cooperating welding engagement anddisengagement, respectively, with the anvil 58. The reciprocating weldhead 56 and anvil 58 cooperate to form the longitudinal seam 54 infabric 16 by welding the respective plies 24, 26 together. It should beappreciated that other means for joining the plies 24, 26 together toform the longitudinal seam 54 such as by stitching, staples or othermeans, are well within the scope of this invention.

The first transport station 62 is located downstream from thelongitudinal seam forming station 52 and includes cooperating upper andlower material feed rollers 63, 65, respectively. The rollers 63, 65rotate in opposite directions, as shown in FIG. 9, to thereby advanceand feed the fabric 16 through the various stations of the system 10.Advantageously, a center region 67 of each roller 63, 65 has a reduceddiameter with respect to the remainder of the roller 63, 65 to allow thecompressed spring 14 to pass between the rollers 63, 65 while stillmaintaining secure contact and engagement between the fabric 16 and theremainder of the feed rollers 63, 65. As the fabric 16 passes betweenthe rollers 63, 65, it is pulled from the supply roll (not shown in FIG.9) through the upstream stations and is advanced toward a springexpansion region 70.

The compressed springs 14 are permitted to relax and expand within thefabric 16 in the spring expansion region 70. The expansion of thesprings 14 in the spring expansion region 70 may be uncontrolled orcontrolled by various mechanisms as previously described herein.

The transverse seam forming station 78 forms the transverse seam 80 inthe fabric 16 between each of the adjacent springs 14 which haveexpanded within the fabric 16 from their initially compressedconfiguration. Preferably, the transverse seam forming station 78includes first and second transverse seam forming members which in oneembodiment includes the transverse seam weld head 82 which reciprocatestoward and away from the fabric 16. The transverse seam weld head 82cooperates with a transverse seam anvil 84 located on an opposite sideof the forming string 12 of pocketed coil springs 14, as shown in FIG.9. According to the embodiment shown in FIG. 9, the anvil 84 is arotating wheel with an axis of rotation generally parallel to thelongitudinal axes 60 of the springs 14. A plurality of arcuate recesses87, six of which are shown in FIG. 9, are on the periphery of the anvilwheel 84 to at least partially surround the pocketed springs 14 as theyadvance through the transverse seam forming station 78. An anvil face 85is formed between each adjacent pair of arcuate recesses 87. Each anvilface 85 cooperates with the transverse weld head 82 to form thetransverse seam 80 between the adjacent springs 14. The rotation of theanvil 84 is synchronized with the reciprocal movement of the weld head82 so that each time the weld head 82 advances toward the forming string12, it cooperates with the rotating anvil 84 to successively form thetransverse seams 80 in cooperation with the successive anvil faces 85.The anvil 84 of FIG. 9 may be rotationally driven to assist in themovement of the string 12 and springs 14 through the system 10.

As a result of the system and method of FIG. 9, the string 12 ofpocketed coil springs 14 is formed with the longitudinal axes 60 of eachof the springs 14 remaining generally parallel to the transverse seams80 in the fabric 16. Due to the expansion of the springs 14, thelongitudinal seam 54 formed at the free edges 28 of the fabric 16 ispositioned generally on the side face 88 of the string 12 between thetop and bottom ends 90, 92 of the pocketed coil springs 14. As such, thepresent invention avoids the need for turning the springs 14 within thefabric pocket as is required in the prior art systems. Moreover, thelongitudinal seam 54 preferably becomes attached to the side face 88when the transverse seam 80 is formed at the transverse seam formingstation 78. Therefore, in the region of the fabric 16 proximate thetransverse seam 80, typically four layers of fabric 16 are seededtogether at the transverse seam forming station 78.

Additionally, the system of FIG. 9 may include the transverse seamconfiguration 80 a, as shown in FIG. 7, or similar arrangement forcontouring the transverse seam 80, 80 a to the shape of barrel-shapedsprings 14 a or other spring configurations as is discussed withreference to FIGS. 7 and 8. The configuration of the transverse seam 80,80 a may be accomplished by appropriately configuring the weld head 82,anvil 84 or the anvil faces 85 of FIG. 9.

From the above disclosure of the general principles of the presentinvention and the preceding detailed description of at least onepreferred embodiment, those skilled in the art will readily comprehendthe various modifications to which this invention is susceptible.Therefore, we desire to be limited only by the scope of the followingclaims and equivalents thereof.

We claim:
 1. A method of forming a string of pocketed coil springscomprising the steps of: feeding a supply of fabric having first andsecond generally parallel plies of the fabric; inserting a series ofcompressed springs between the first and second plies; joining the firstand second plies together to form a longitudinal seam proximate freeedges of the first and second plies opposite from the longitudinal foldline; allowing the springs to at least partially expand within thefabric so that a longitudinal axis of each of the springs is generallyperpendicular to the longitudinal seam of the fabric; controlling theexpansion of the springs by a pair of spaced rotating members with thesprings therebetween; wherein the axes of rotation of the rotatingmembers are generally perpendicular to the longitudinal axes of thesprings and each rotating member comprises a band passing over spacedrollers; wherein a separation distance between the bands increases in adownstream direction to thereby control the expansion of the springsbetween the bands; engaging the fabric with a plurality of projectionsextending from at least one of the bands; and forming a transverse seamin the fabric generally parallel to the longitudinal axis of the springsand between adjacent springs to thereby enclose each of the springswithin a fabric pocket.
 2. The method of claim 1 wherein the springs areallowed to at least partially expand prior to forming the transverseseam and after joining the first and second plies to form thelongitudinal seam.
 3. The method of claim 1 wherein the joining andforming steps are performed by welding the fabric together.
 4. Themethod of claim 1 further comprising: pulling the fabric with at leastone rotating transport member located downstream from a position atwhich the longitudinal seam is formed, the rotating transport membercomprises a plurality of arcuate shaped recesses which at leastpartially surround each spring.
 5. The method of claim 1 wherein thelongitudinal seam is positioned generally on the side of the springsbetween top and bottom ends thereof and tacked to the side of the pocketin the formed string of pocketed coil springs.
 6. The method of claim 1wherein the orientation of the longitudinal axes of the springs remainsgenerally unaltered during the entire process.
 7. The method of claim 1wherein the inserting further comprises inserting compressed springswhich have a generally non-linear shaped profile and the forming of thetransverse seam further comprises forming the transverse seam togenerally correspond to at least a portion of the profile of theadjacent springs.
 8. The method of claim 1 wherein the recited steps areperformed sequentially in the order recited in claim
 1. 9. The method ofclaim 1 wherein the forming of the transverse seam includes a first anda second transverse seam forming member which are located on oppositesides of the fabric and cooperate to form the transverse seam, theforming further comprising: rotating the first transverse seam formingmember.
 10. The method of claim 9 further comprising: reciprocating thesecond transverse seam forming member toward and away from the firsttransverse seam forming member; and synchronizing the rotating andreciprocating of the first and second transverse seam forming members,respectively, for forming the transverse seam.
 11. The method of claim 1wherein the projections are nibs and the nibs are arranged in at leastone row oriented generally parallel with a direction of travel of theband.
 12. The method of claim 1 wherein the engaging of the fabric withthe projections does not substantially inhibit the expansion of thesprings.
 13. The method of claim 1 wherein the bands each form an angleof less than about 45° with respect to a longitudinal axis of thestring.
 14. The method of claim 13 wherein the angle is about 10°.
 15. Amethod of forming a string of pocketed coil springs comprising the stepsof: feeding a supply of fabric having first and second generallyparallel plies of the fabric; inserting a series of compressed springsbetween the first and second plies; joining the first and second pliestogether to form a longitudinal seam proximate free edges of the firstand second plies opposite from the longitudinal fold line; allowing thesprings to at least partially expand within the fabric so that alongitudinal axis of each of the springs is generally perpendicular tothe longitudinal seam of the fabric; engaging the fabric with aplurality of moving projections to thereby control the movement of thefabric and the partial expansion of the springs within the fabric; andforming a transverse seam in the fabric between adjacent springs tothereby enclose each of the springs within a fabric pocket.
 16. Themethod of claim 15 wherein the projections are nibs projecting from amember moving in a closed path.
 17. The method of claim 16 wherein thenibs are arranged in at least one row oriented generally parallel with adirection of travel of the member moving in a closed path.
 18. Themethod of claim 15 wherein the moving projections assist in advancingthe fabric.
 19. The method of claim 15 wherein the transverse seam isformed generally parallel to the longitudinal axis of the springs. 20.The method of claim 15 wherein the moving projections assist incontrolling the expansion of the springs within the fabric.
 21. A systemfor forming a string of pocketed coil springs, each of the springs beingenclosed within a pocket formed of fabric, the system comprising: aspring insertion station at which compressed springs are individuallyinserted between first and second plies of the fabric; a longitudinalseam forming station located downstream from the spring insertionstation, the longitudinal seam forming station joining the first andsecond plies of the fabric together to form a longitudinal seamproximate free edges of the first and second plies; a spring expansionstation located downstream from the longitudinal seam forming station,the spring expansion station permitting the springs to at leastpartially expand between the first and second plies with a longitudinalaxis of each spring being generally perpendicular to the longitudinalseam; a transverse seam forming station located downstream from thelongitudinal seam forming station, the transverse seam forming stationforming a transverse seam in the fabric to separate each pair ofadjacent springs and thereby enclose each of the springs within a fabricpocket when inserted therein; and a transport station which advances thefabric and springs contained therein through the respective stations;wherein the spring expansion station further comprises at least onemoving member having a plurality of projections engaging the fabric tothereby assist in movement of the fabric and springs contained therein.22. The system of claim 21 wherein the spring expansion station furthercomprises a pair of spaced rotating members with the springstherebetween.
 23. The system of claim 22 wherein the axes of rotation ofthe rotating members are generally perpendicular to the longitudinalaxes of the springs and each rotating member further comprises a bandpassing over spaced rotational mounted rollers, wherein the projectionsproject from at least one of the bands and a separation distance betweenthe bands increases in a downstream direction to thereby control theexpansion of the springs between the bands.
 24. The system of claim 21wherein the transverse seam forming station produces a transverse seamwhich substantially conforms to a non-linear profile of the adjacentspring.
 25. A system for forming a string of pocketed coil springs, eachof the springs being enclosed within a pocket formed of fabric, thesystem comprising: a spring insertion station at which compressedsprings are individually inserted between first and second plies of thefabric folded about a longitudinal fold line; longitudinal seam formingstation located downstream from the spring insertion station, thelongitudinal seam forming station including a cooperating thermal weldhead and anvil to thermally weld the first and second plies of thefabric together to form a longitudinal seam proximate free edges of thefirst and second plies opposite from the longitudinal fold line; aspring expansion station located downstream from the longitudinal seamforming station, the spring expansion station including a pair ofrotating members on opposite sides of the springs within the fabric topermit the springs to at least partially expand between the first andsecond plies so that a longitudinal axis of each spring is generallyperpendicular to the longitudinal seam; a plurality of nibs projectingfrom at least one of the bands to engage the fabric; a transverse seamforming station located downstream from the spring expansion station,the transverse seam forming station including a cooperating thermal weldhead and anvil to thermally weld a transverse seam in the fabric betweeneach pair of adjacent springs to thereby enclose each of the springswithin a fabric pocket when inserted therein; and a transport stationwhich advances the fabric and springs contained therein through therespective stations.